3

I'm trying to get the start/End points of a Shapefile which geometry type is lines, using Shapely.

Here's what I tried :

import geopandas
from shapely.geometry import *
import fiona

schema = {
'geometry': 'Point',
'properties': {'id': 'int'},
}
for line in fiona.open("./Shapefiles/tl.shp"):
# Write a new Shapefile
with fiona.open('./Outputs/result.shp', 'w', 'ESRI Shapefile', schema) as c:
    startEndPoints = Point(line['geometry']['coordinates'][0]), Point(line['geometry']['coordinates'][-1])
    c.write({
        'geometry': mapping(startEndPoints),
        'properties': {'id': 'int'},
    })

After running the script I got this error :

Traceback (most recent call last):
File "C:/Users/User/Documents/Scripts/startEndPoints.py", line 15, in <module>
'geometry': mapping(startEndPoints),
File "C:\Program Files (x86)\Python27\lib\site-packages\shapely\geometry\geo.py", line 75, in mapping
return ob.__geo_interface__
AttributeError: 'tuple' object has no attribute '__geo_interface__'

Process finished with exit code 1

Any idea on what the problem is? Am I missing something?

By the way if I just put :

from shapely.geometry import Point
import fiona
for line in fiona.open("./Shapefiles/tl.shp"):
print Point(line['geometry']['coordinates'][0]), Point(line['geometry']['coordinates'][-1])

I get the results :

POINT (-122.4136252231131 37.77444689220926) POINT (-122.4123122222042 37.77339989262978)
POINT (-122.4166172233352 37.77561789207194) POINT (-122.4168352231301 37.77544489272536)
POINT (-122.4254669503756 37.80586514841474) POINT (-122.4253414477887 37.80523738337594)
POINT (-122.4120802227251 37.77329289282841) POINT (-122.4116882221326 37.77360289269223)
POINT (-122.403928221227 37.76968489249516) POINT (-122.4038392206211 37.7686898923368)
POINT (-122.4034062214653 37.77768889337421) POINT (-122.402952221485 37.77804389367528)
POINT (-122.4083362215629 37.77378789309976) POINT (-122.4073822219715 37.77454389279772)
POINT (-122.3988001599508 37.77642529193749) POINT (-122.4004541112463 37.77511695816931)
POINT (-122.3995072203815 37.7666648926454) POINT (-122.3991442197841 37.76637989275558)
POINT (-122.3954705174111 37.75052611064412) POINT (-122.3954953388096 37.75079277249778)
POINT (-122.4096502215665 37.77017689206735) POINT (-122.4086142215983 37.76934889254507)
POINT (-122.40679422218 37.77255089251806) POINT (-122.4065396542004 37.77275206969875)
POINT (-122.3911729658918 37.76952536147485) POINT (-122.3910978699473 37.76875434317915)
POINT (-122.408514985576 37.76433570878993) POINT (-122.4084132127141 37.76323936432929)
....
Process finished with exit code 0

My only problem is saving these endpoints in another shapefile. Any ideas?


I managed to solve the problem with a workaround actually. What I did is save the startPoints and endPoints each in a different shapefile. Here's my code :

from shapely.geometry import *
import fiona

schema = {'geometry': 'Point' }
with fiona.open("./TLShapefile/TimeLimits.shp") as input:
    input.schema['geometry'] = "Point"
    # write the startPoint shapefile
    with fiona.open('./Outputs/endPoints.shp', 'w', 'ESRI Shapefile', input.schema.copy(), input.crs) as output:
    for line in input:
        geom = shape(line['geometry'])
        # Write a new Shapefile for the startPoints, do the same thing for endPoints afterwards
        startPoints = Point(line['geometry']['coordinates'][0])
        #endPoints = Point(line['geometry']['coordinates'][-1]) #For the end points
        elem['geometry'] = mapping(startPoints)
        #elem['geometry'] = mapping(endPoints) #For the end points
        output.write(elem)

Now I have seperate shapefiles for the start points and the end points. Although my main goal is to get one shapefile with the startpoints and endpoints all together.


I have updated my code based on Gene's answer, using Shapely :

from shapely.geometry import *
import fiona

schema = {
'geometry': 'Point',
'properties': { 'AGENCY': 'str',
                'CONFLICT' :'int',
                'CREATED_DA' :'str',
                'CREATED_US' :'str',
                'CREATED__1' :'str',
                'CREATED__2' :'str',
                'DAYS' :'str',
                'EDITOR' :'str',
                'ENACTED' :'str'
with fiona.open("tl.shp") as input:
    # write the startPoint shapefile
    with fiona.open('./Outputs/startEndPoints.shp', 'w', 'ESRI Shapefile', schema, input.crs) as output:
    for line in input:
        startEndPoints = MultiPoint([line['geometry']['coordinates'][0],  line['geometry']['coordinates'][-1]])
        for point in startEndPoints:
        output.write({'geometry': mapping(point), 'properties': {
                'AGENCY': 'str',
                'CONFLICT' :'int',
                'CREATED_DA' :'str',
                'CREATED_US' :'str',
                'CREATED__1' :'str',
                'CREATED__2' :'str',
                'DAYS' :'str',
                'EDITOR' :'str',
                'ENACTED' :'str'}})

When I run the script now I get this :

Process finished with exit code -1073741819 (0xC0000005)
3
  • 2
    You define a schema (dictionary) with 'CONFLICT' :'int (one field of the shapefile) ,for example, and you write a value in the table 'CONFLICT' :56 (row value) and not the repetition of the field definition as value – gene Jul 22 '16 at 15:38
  • @gene Are those values going to be added to the output? – GeoSal Jul 22 '16 at 15:45
  • Yes, you define a field of the table and after you add a geometry and a value for each row of the table – gene Jul 22 '16 at 16:32
5

Why import geopandas if you don't use it ? (GeoPandas = Pandas + Fiona + Shapely)

1) Following the suggestion of bugmenot123

The schema for a MultiLineString

schema = {
'geometry': 'MultiPoint',
'properties': {'id': 'int'},
 }

And

with fiona.open("lines.shp") as inp:
    with fiona.open('result.shp', 'w', 'ESRI Shapefile', schema) as out:
       for line in inp:
           startEndPoints = MultiPoint([line['geometry']['coordinates'][0],  line['geometry']['coordinates'][-1]])
           out.write({'geometry': mapping(startEndPoints),'properties': {'id': 1}})

2) But a shapefile has no MultiPoint schema geometries: a shapefile that indicates Point in its schema may yield either Point or MultiPoint features (simple list of Point).

Therefore:

schema = {
'geometry': 'Point',
'properties': {'id': 'int'},
 }
with fiona.open("lines.shp") as inp:
with fiona.open('result2.shp', 'w', 'ESRI Shapefile', schema2) as out:
    for line in inp:
        startEndPoints = MultiPoint([line['geometry']['coordinates'][0],  line['geometry']['coordinates'][-1]])
        for point in startEndPoints: 
           out.write({'geometry': mapping(point),'properties': {'id': 1}})

3) Now, if you want to use GeoPandas only

import geopandas as gpd
from geopandas.geoseries import Point
lines = gpd.GeoDataFrame.from_file("lines.shp")
startpts = gpd.GeoSeries([Point(list(pt['geometry'].coords)[0]) for i,pt in lines.iterrows()])
endpts = gpd.GeoSeries([Point(list(pt['geometry'].coords)[-1]) for i,pt in lines.iterrows()])
points = startpts.append(endpts)
result = gpd.GeoDataFrame(points,columns=['geometry'])
# add a field
result['id']= result.index
# save the resulting shapefile
result.to_file("res_geopandas.shp")  

New

 # columns of the GeoDataframe line
 print lines.columns.values
 [u'AFFLEUR' u'IDENT' u'NATURE' 'geometry']
 print lines['IDENT']
 0    3560025
 1    3560023
 2    3560024
 Name: IDENT, dtype: int64

Suppose that I want to add the IDENT column to the results

  # create a GeoDataFrame with the startpts GeoSerie
  dfstartpts = gpd.GeoDataFrame(startpts,columns=['geometry'])
  # add a column and copy the values of IDENT
  dfstartpts['ident'] = lines['IDENT']
  # same for the endpoints
  dfendpts = gpd.GeoDataFrame(endpts,columns=['geometry'])
  dfsendpts['ident'] = lines['IDENT']
  # "merge" the dataframes
  result = dfstartpts.append(dfendpts)
  print result.columns.values
  ['geometry' 'ident']
  print result['ident']
  0    3560025
  1    3560023
  2    3560024
  0    3560025
  1    3560023
  2    3560024
  Name: ident, dtype: int64
8
  • Thank you again for your detailed answer @gene! I just saw it. I actually just posted an answer below to my post with a workaround that I managed to do. Please refer to it. As for ur suggestions I just tried the second one and I had this error : ValueError: Record does not match collection schema: ['id'] != [u'CREATED_DA', u'CREATED_US', u'RPPAREA3', ..... The error comes from this line : out.write({'geometry': mapping(point),'properties': {'id': 1}}) – GeoSal Jul 22 '16 at 12:43
  • 1
    The error comes with the fields of the shapefile that not match the shapefile schema. The schema presented here is with one field that contains an integer and no other thing ('id': 1). If you want other fields, you need to add them to the schema. – gene Jul 22 '16 at 12:56
  • I updated my post please refer to my last code. I added the other fields indeed and I get this error now : Process finished with exit code -1073741819 (0xC0000005) – GeoSal Jul 22 '16 at 14:52
  • Tried ur 3rd suggestion using Geopandas and it works perfectly ! The only thing is that the output gets projected in a different place. Even if I add the line regarding the transformation of the input using to_crs – GeoSal Jul 22 '16 at 15:20
  • 1
    look at New in my answer – gene Jul 22 '16 at 16:53
0

You are trying to save two Point objects into a schema that wants one Point. You could either use MultiPoint instead or construct a linestring for each start-end pair.

5
  • Thank u for ur answer. I tried replacing Point in the schema with Multipoint, but I'm still having the same error. – GeoSal Jul 22 '16 at 8:57
  • I just replaced Point(line['geometry']['coordinates'][0]), Point(line['geometry']['coordinates'][-1]) with MultiPoint(line['geometry']['coordinates'][0]), MultiPoint(line['geometry']['coordinates'][-1]) , and now I have this error : AttributeError: 'float' object has no attribute '_ndim' – GeoSal Jul 22 '16 at 9:01
  • I am not entirely sure what your end goal is, could you extend your question? Do you just need all the points or do you need to know which two belong(ed) together or do you need to know which ones are start points and end points or do you need to know which ones are start and end point pairs? – bugmenot123 Jul 22 '16 at 11:26
  • My end goal is to save the the startpoints and endpoints all together in one shapefile. – GeoSal Jul 22 '16 at 12:53
  • I will be projecting these points later on a lines' shapefile the splitting these lines on the start/end points – GeoSal Jul 22 '16 at 13:03

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